Mistletoe is often regarded as a parasite of shrubs and trees however Mistletoe produces its energy through photosynthesis and functions only in a semi-parasitic mode. Continuing studies are demonstrating the importance of mistletoe for biodiversity in degraded bushland (Watson & Herring 2006).
Too often we see the wonders of fauna or flora as isolated observations and miss the complexity and beauty of the co-evolutionary relationships. Mistletoe is a good example to illustrate some of these inter-dependencies.
At least four species of Mistletoe occur around the Wedderburn/Mount Korong locality and one, the Grey Mistletoe (Amyema quandang) can be seen on Cootamundra Wattle (Acacia bayleania) in gardens around Wedderburn and is common on Deane’s Wattle (Acacia deanei ssp. paucijuga) and Wallowa (Acacia euthycarpa) around Mount Korong. Images in Figs 1 to 10 were taken near Mt. Korong and Wedderburn by D. Stewart.
The flower structure of Mistletoe is designed to transfer pollen to and from the head of visiting honeyeaters such as New Holland Honeyeaters (Fig 3) commonly seen attending the flowers. Mistletoe Birds follow the fruiting cycle of mistletoe species and consume the fruit. The digestive system of Mistletoe Birds is modified to facilitate rapid transit of ingested fruit and the bird’s behavior is adapted to increase the chance of seed falling to a suitable growth position on a host plant. These birds perch atop the host tree and frequently turn parallel to the perch twig prior to voiding the seed which emerges like a necklace of pearls, to slowly drip down through the foliage Fig 4.
Figs 5 to 10 illustrate some of the Lepidoptera dependent on mistletoe as the food plant for their larvae.
Fig 10 is of an Ogyris butterfly whose larvae are dependent on the attendance by certain ant species. The butterfly has brilliant iridescent metallic blue upper wing surfaces that flash in the sunlight and are hidden from view as the insect keeps wings together when perched on the mistletoe.
The obvious thought to ponder when considering these examples of interdependent associations is which species is dependent on which other species for ongoing function of this component of the ecosystem?
Article and photos by David Stewart, former President of the Victorian Entomological Society.
Figure 1: Grey Mistletoe (Amyema quandang).
Figure 2: Ripe fruit of Grey Mistletoe.
Figure 3: New Holland Honeyeater (Phylidonyris novaehollandiae)
Figure 4: Male Mistletoebird (Dicaeum hirundinaceum) delivering seed.
Figure 5: Spotted Jezabel (Delias aganippe) laying on Grey Mistletoe.
Figure 6: Eggs of Spotted Jezabel.
Figure 7: Spotted Jezabel Larvae.
Figure 8: Pupae and recently emerged adult.
Figure 9: Mistletoe moth.
Figure 10: Satin Azure (Ogyris amaryllis meridionalis).